verb (used with object)
- to make different in some particular, as size, style, course, or the like; modify: to alter a coat; to alter a will; to alter course.
- to castrate or spay.
verb (used without object)
- to change; become different or modified.
- to make or become different in some respect; change
- (tr) informal, mainly US a euphemistic word for castrate, spay
late 14c., “to change (something),” from Old French alterer “change, alter,” from Medieval Latin alterare “to change,” from Latin alter “the other (of the two),” from PIE *al- “beyond” (see alias (adv.)) + comparative suffix -ter (cf. other). Intransitive sense “to become otherwise” first recorded 1580s. Related: Altered; altering.